Planet

Planets were objects orbiting stars, that massive enough to generate sufficient gravity to form a spherical shape. They orbited nearly every star in the known galaxy, and were usually places where life evolved, stars being too hot and outer space being too cold. There were more than 1 trillion planets in the Galaxy.

Formation
Planets formed within protoplanetary disks that surrounded young stars. Sand and dust within these disks coalesced into rocks, which themselves coalesced to form larger and larger objects. Eventually, the gravity from these bodies would draw in more and more matter, causing an exponential increase in mass. When sufficient mass had been attained, gravitational forces would crush the planet into a spherical shape.

Planets began to form within a few million years of the creation of the Universe, although most of the first planets were obliterated when their stars died in supernovae. The oldest surviving planet in the Galaxy was Juldice, the original homeworld of the Celestials.

Size
Larger than dwarf planets and asteroids, planets were defined as having a mass in excess of 0.01 SPM.

Objects smaller than this were considered dwarf planets, and objects too small to be spherical were termed asteroids.

Objects larger than 10 SPM were considered giant planets, and they often had massive atmosphere surrounding their rocky cores.

Objects sufficiently massive to trigger nuclear fusion were deemed brown dwarfs, and those large enough to maintain it were considered stars.

Objects orbiting other planets instead of stars were known as moons, and those that orbited no object, and floated freely in space, were known as planemos.

Variety
Planets ranged from airless rocks to balls of ice to gas giants and terrestrial worlds teeming with life. Planets often had natural satellites, called moons.

Notable Planets
See Category:Planets for a full list of planets.